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Abstract:

The present invention relates to expandable scaffolds such as stents. The
vascular scaffolds may be formed from bioabsorbable polymers, metals or
various combinations of metals and polymers. The stents of the present
invention comprise a generally cylindrically shaped main body having a
plurality of expandable first and second circumferential elements. The
body of the vascular scaffold comprises a plurality of circumferential
elements. At least two circumferential elements may be connected to form
a pair of circumferential elements. There may be one or more connections
between the circumferential elements forming the pair. Each pair of
circumferential elements is connected to an adjacent pair of
circumferential elements by at least one connection element. When
expanded, at least a portion of the connection elements connecting the
circumferential elements in the pairs and/or the connection elements
connecting the circumferential elements in adjacent pairs form a
contiguous spiral pattern which may form a helix(s).

Claims:

1. A scaffold comprising a plurality of circumferential elements, wherein
at least two circumferential elements are connected by a plurality of
first connection elements to form a pair of circumferential elements, one
pair of circumferential elements being connected to an adjacent pair of
circumferential elements by a plurality of second connection elements,
and when the scaffold is expanded, at least a portion of the first and/or
second connection elements form at least one contiguous spiral pattern.

2. The scaffold of claim 1, wherein the circumferential elements comprise
a plurality of undulations.

3. The scaffold of claim 2, wherein the undulations form a sinusoidal
pattern.

4. The scaffold of claim 3, wherein the sinusoidal pattern is repeating.

5. The scaffold of claim 3, wherein the sinusoidal pattern is
non-repeating.

6. The scaffold of claim 1, wherein there are at least two first
connection elements connecting the pair of circumferential elements.

7. The scaffold of claim 1, wherein there are three first connection
elements.

8. The scaffold of claim 1, wherein there are three second connection
elements.

9. The scaffold of claim 3, wherein the sinusoidal pattern of one
circumferential element in the pair is 180.degree. degrees out-of-phase
with the sinusoidal pattern of the other circumferential element in the
pair.

10. The scaffold of claim 2, wherein each peak of the undulation in one
circumferential element of the pair is connected with each valley in the
second circumferential element in the pair by the first connection
element.

11. The scaffold of claim 1, wherein the first connection element is
linear.

12. The scaffold of claim 1, wherein the first connection element is
S-shaped or Z-shaped.

13. The scaffold of claim 1, wherein the first connection element
contains a marker dot.

14. The scaffold of claim 3, wherein the sinusoidal patterns of one pair
of circumferential elements is in-phase with the sinusoidal pattern of an
adjacent pair of circumferential elements.

15. The scaffold of claim 2, wherein every other peak of the undulation
in one circumferential element in one pair is connected by the second
connection element to the valley of the corresponding undulation in the
circumferential element in the adjacent pair of circumferential elements.

16. The scaffold of claim 1, wherein the second connection element is
S-shaped or Z-shaped.

17. The scaffold of claim 1, wherein the second connection element is
curvilinear.

18. The scaffold of claim 1, wherein the spiral pattern comprises at
least one first connection element and at least one second connection
element.

19. The scaffold of claim 1, wherein the spiral pattern comprises at
least one first connection element.

20. The scaffold of claim 1, wherein the spiral pattern comprises at
least one second connection element.

21. The scaffold of claim 1, wherein the spiral pattern forms a helix.

22. The scaffold of claim 21, wherein there are two helices parallel to
each other.

23. The scaffold of claim 21, wherein there are two helices equidistant
from the cylindrical axis of the scaffold.

26. The scaffold of claim 1, wherein the scaffold comprises a
biocorrodable metal.

27. The scaffold of claim 26, wherein the biocorrodable metal is iron or
magnesium.

28. The scaffold of claim 1, wherein the scaffold is in an expanded
state.

29. The scaffold of claim 1, wherein the scaffold is in an
as-manufactured state.

30. The scaffold of claim 1, wherein the length of the second connection
element is greater than the length of the first connection element.

31. The scaffold of claim 1, wherein the length of the second connection
element is less than the length of the first connection element.

32. The scaffold of claim 1, wherein the length of the second connection
element is equal to the length of the first connection element.

33. The scaffold of claim 1, wherein the spiral pattern is formed from a
repeated unit comprising, the first connection element and second
connection element.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application
No. 61/716,660 filed on Oct. 22, 2012, the content of which is
incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to stents. In particular, the present
invention relates to geometric designs of stents which exhibit a high
degree of radial strength and flexibility and which can be formed from
bioabsorbable polymers.

BACKGROUND OF THE INVENTION

[0003] Stents are vascular scaffolds that are positioned in diseased
vessel segments to support the vessel walls. During angioplasty, stents
are used to repair and reconstruct blood vessels. Placement of a stent in
the affected arterial segment prevents elastic recoil and closing of the
artery. Stents also prevent local dissection of the artery along the
medial layer. Physiologically, stents may be placed inside the lumen of
any space, such as an artery, vein, bile duct, urinary tract, alimentary
tract, tracheobronchial tree, cerebral aqueduct or genitourinary system.
Stents may also be placed inside the lumen of non-human animals, such as
primates, horses, cows, pigs and sheep.

[0004] In general, there are two types of vascular scaffolds or stents:
self-expanding and balloon-expandable. Self-expanding stents
automatically expand once they are released and assume a deployed,
expanded state. A self-expanding stent is placed in the vessel by
inserting the stent in a compressed state into the affected region, e.g.,
an area of stenosis. Compression or crimping of the stent can be achieved
using crimping equipment (see,
http://www.machinesolutions.org/stent_crimping.htm, April, 2009). The
stent may also be compressed using a tube that has a smaller outside
diameter than the inner diameter of the affected vessel region. Once the
compressive force is removed or the temperature raised, the stent expands
to fill the lumen of the vessel. When the stent is released from
confinement in the tube, the stent expands to resume its original shape,
in the process becoming securely fixed inside the vessel against the
wall.

[0005] A balloon-expandable stent is expanded using an inflatable balloon
catheter. Balloon-expandable stents may be implanted by mounting the
stent in an unexpanded or crimped state on a balloon segment of a
catheter. The catheter, after having the crimped stent placed on it, is
inserted through a puncture in a vessel wall and moved through the vessel
until it is positioned in the portion of the vessel that is in need of
repair. The stent is then expanded by inflating the balloon catheter
against the inside wall of the vessel. Specifically, the stent is
plastically deformed by inflating the balloon so that the diameter of the
stent is increased and the stent expanded.

[0006] There are functional limitations common to many stents. These
include, for example, comparative rigidity of the stent in a crimped as
well as deployed state, and limited flexibility making delivery and
placement in narrow vessels difficult. The present invention provides a
geometric design for a stent that offers both a high degree of
flexibility and significant radial strength. The stent may also be formed
from bioabsorbable polymers. The design of this stent also allows it to
be inserted into small diameter vessels having tortuous vascular anatomy.

SUMMARY OF THE INVENTION

[0007] The present scaffold may comprise a plurality of circumferential
elements, where at least two circumferential elements are connected by a
plurality of first connection elements to form a pair of circumferential
elements, one pair of circumferential elements is connected to an
adjacent pair of circumferential elements by a plurality of second
connection elements. When the scaffold is expanded, at least a portion of
the first and/or second connection elements form at least one contiguous
spiral pattern. The spiral pattern may comprise at least one first
connection element, at least one second connection element, or at least
one first connection element and at least one second connection element.

[0008] The circumferential elements can be comprised of a plurality of
undulations. In certain embodiments, the undulations form a repeating or
non-repeating sinusoidal pattern. There may be at least two first
connection elements connecting the pair of circumferential elements. In
one embodiment, there are three first connection elements connecting the
pair of circumferential elements. In another embodiment, there are three
second connection elements connecting adjacent pairs of circumferential
elements.

[0009] The sinusoidal pattern of one circumferential element in the pair
may be 180° degrees out-of-phase with the sinusoidal pattern of
the second circumferential element in the pair. Each peak of the
undulation in one circumferential element of the pair may be connected by
the first connection element with each valley in the second
circumferential element in the pair.

[0010] The sinusoidal patterns of one pair of circumferential elements may
be in-phase with the sinusoidal pattern of an adjacent pair of
circumferential elements. Every other peak of the undulation in one
circumferential element in one pair may be connected by the second
connection element to the valley of the corresponding undulation in the
circumferential element in the adjacent pair of circumferential elements.

[0011] The first connection element can be linear, S-shaped or Z-shaped.
It may contain a marker dot.

[0012] The second connection element can be curvilinear, S-shaped or
Z-shaped. It may contain a marker dot. The length of the second
connection element can be greater than, equal to or less than the length
of the first connection element.

[0013] When expanded, the spiral pattern can form a helix. If there are
two helices, they may or may not be substantially parallel to each other.
In one embodiment, there are two or more helices equidistant from the
cylindrical axis of the scaffold. The spiral pattern can be formed from a
repeated unit comprising the first connection element and second
connection element. The scaffold may comprise bioabsorbable polymeric
material, a biocorrodable metal or combinations thereof. Non-limiting
examples of bioabsorbable polymeric material include poly-L-lactide
(PLLA). Non-limiting examples of biocorrodable metals including iron and
magnesium. The scaffold can be in an expanded, partially expanded,
unexpanded, or as manufactured state.

[0031]FIG. 12 illustrates the functionality of the connection element.

[0032]FIG. 13 illustrates the geometry of the scaffold and connection
elements (first and second connection elements) on expansion.

[0033] FIGS. 14A and 14B illustrate the geometry of the connection
elements.

[0034]FIG. 14c shows various embodiments of how the connection elements
can be attached to adjacent circumferential elements.

[0035] FIGS. 15A-E illustrates where the connection elements can attach
along the undulations.

[0036]FIG. 16 shows the radial displacement of the attachment of
connection element to adjacent undulations.

[0037] FIGS. 17A and 17B show an example of phasing in adjacent
circumferential elements.

[0038]FIG. 18 shows a cut pattern of another embodiment of the scaffold
where there are three first connection elements between two
circumferential elements.

[0039]FIG. 19A shows a cut pattern of another embodiment of the scaffold.
In this embodiment, there are three first connection elements between two
circumferential elements, and the circumferential elements are comprised
of a plurality of linear segments.

[0040] FIGS. 19B-19E show detailed views of parts of the scaffold in FIG.
19A.

[0043] The present invention relates to expandable vascular scaffolds
including stents. The overall design of the scaffold is based on a
modular design that comprises pairs of circumferential elements connected
by one or more connection elements (the terms connecting and connection
are used interchangeably here). Using a modular approach, the scaffold
can be assembled from circumferential elements and connection elements
that vary in length and design. When expanded, the connection elements
form a spiral pattern, which can be a helix.

[0044] The vascular scaffolds may be formed from a bioabsorbable polymer,
a biocorrodable metal, or combinations thereof. Non-limiting examples of
bioabsorbable polymers include poly-L-lactide (PLLA), poly-D-lactide
(PDLA), poly(D,L-lactide) (PDLLA), poly(desaminotyrosil-tyrosine ethyl
ester) carbonate, poly(caprolactone) (PCL), and poly(anhydride ester)
salicylic acid. Non-limiting examples of biocorrodable metal include
iron, magnesium, and magnesium alloy. The scaffolds may also be formed
from various combinations of metals and polymers. U.S. Pat. Nos.
7,846,361; 7,897,224 and 8,137,603. U.S. Patent Publication No.
2010/0093946. Alexy, et al., BioMed Research International, 2013, Article
ID 137985.

[0045] Generally, the scaffold is a cylindrical object having a
cylindrical axis running the length of the cylinder. The modular
geometric design of the present invention exhibits a high degree of
flexibility and significant radial strength. Generally, the scaffolds
have a primarily cylindrical shaped main body that has a plurality of
expandable circumferential elements. The circumferential elements can
vary in length. At least two circumferential elements may be connected to
form a pair of circumferential elements. There may be one or more
connection elements between the circumferential elements forming the pair
of circumferential elements. The connection elements may be found in a
variety of different geometric shapes, including linear, curvilinear or
combinations of the two shapes. Each pair of circumferential elements is
connected to an adjacent pair of circumferential elements by at least one
connection element. The number of connection elements between
circumferential elements in a pair or between pairs of circumferential
elements can vary.

[0046] As used herein, the term "circumferential elements" refers to
structural elements circumscribing the circumference of the present
scaffold which may be in the form of a cylinder. In one embodiment, the
circumferential element is bounded by two hypothetical planes which are
substantially perpendicular to the cylindrical axis of the scaffold. A
circumferential element may comprise (or consist of) a plurality of
undulations.

[0047] When the vascular scaffold is expanded, at least a portion of the
connection elements connecting the circumferential elements in the pairs
and/or the connection elements connecting the circumferential elements in
adjacent pairs form a contiguous spiral pattern.

[0048] In one embodiment, the contiguous spiral pattern is oriented
substantially parallel to the cylindrical axis of the scaffold. The
contiguous spiral pattern may also take other orientations. The
contiguous spiral pattern may form a helix and there may be one or more
helices in a particular embodiment, e.g., double or triple helix, or 4,
5, 6 or higher numbers of helices. When there is more than one helix,
adjacent helices may be substantially parallel to each other. Adjacent
helices may not be parallel to each other. In one embodiment, there are
two or more helices equidistant from the cylindrical axis of the
scaffold.

[0049] The circumferential elements may be uniform in shape. Alternatively
a circumferential element may be comprised of a variety of different
shapes. For example, the circumferential elements may be formed from a
series of undulations which may be in a sinusoidal pattern, a sawtooth
pattern, a square wave pattern or any other type of repeating or
non-repeating pattern, e.g., a combination of sinusoidal and sawtooth.
The amplitude of the undulations may vary within one circumferential
element or between two circumferential elements (amplitude is the peak
deviation of the function from zero). The amplitude and frequency of the
undulations can also vary. For example, a circumferential element can be
comprised of a sinusoidal pattern having a repeated pattern of varying
amplitudes, 2:1:2:1, 2:1, etc., where, the ratio of the amplitudes of the
undulations are represented by the ratio shown. Other ratios are also
possible, 3:1, 4:1, 5:1, etc. The circumferential elements may be
comprised of one or more segments with each segment having its own
undulation pattern. The number of segments in each circumferential
element may vary from 1 to N, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
Thus, the circumferential element can be assembled in a modular fashion
from various segments which may be alike or different. In the scaffold,
the length of all the circumferential elements may be the same.
Alternatively, the length of the circumferential elements may vary, e.g.,
in several different ways. For example, the length of the circumferential
elements within one pair may be the same, while the length of the
circumferential elements closer to one end of the scaffold may be greater
than or less than the length of the circumferential elements closer to
the middle of the scaffold.

[0050] The number of connection elements connecting adjacent
circumferential elements (first connection element, or second connection
element) can range from 1 to N, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or
higher numbers, 10-20. The shape of the connecting elements may be
linear, curvilinear, S-shaped, reverse S-shaped, Z-shaped, reverse
Z-shaped, or any other combination of shapes, including, for example, a
linear and curvilinear section. Similarly, the number of connecting
elements connecting adjacent pairs of circumferential elements may range
from 1 to N (e.g., 1, 2, 3,4, 5, 6, 7, 8, 9 or 10) and the shape of such
connecting elements may be linear, curvilinear, S-shaped, reverse
S-shaped, Z-shaped, reverse Z-shaped, or any combination thereof. The
connecting elements may assume a variety of angles relative to the
cylindrical axis of the scaffold, including, 0-20°, 20-40°,
40-60° or 60-80°; furthermore, the angle of these
connecting elements may be positive or negative relative to the
cylindrical axis of the scaffold. If the connecting elements are
curvilinear, they may be concave and convex with the curvature present at
selected portions of the connecting elements; the degree of curvature may
also vary within one connecting element. The number of connecting
elements can be adapted to modify the flexibility of the scaffold with
decreasing flexibility generally being present as the number of
connecting elements increases.

[0051] When the connection element is S-shaped, it may have a
substantially S-shaped structure. In one embodiment, the S-shaped
connection elements have a double curved structure which allows for more
slack between circumferential elements, enabling greater expansion of the
scaffold. The longer this S-shaped segment, the more slack and
expandability there is in the structure. An S-shaped connection element
may be smooth or may be angular. In another embodiment, the S-shaped
connection element includes at least three substantially linear portions:
a first linear portion being substantially parallel to the cylindrical
axis of the scaffold (e.g., forming an angle between about 0 degree and
about 20 degrees with respect to the cylindrical axis of the scaffold); a
second linear portion being substantially perpendicular to the axis
(e.g., forming an angle between about 70 degree and about 90 degrees with
respect to the cylindrical axis of the scaffold); and a third linear
portion being substantially parallel to the axis (e.g., forming an angle
between about 0 degree and about 20 degrees with respect to the
cylindrical axis of the scaffold). In still another embodiment, the
S-shaped connection element includes at least three substantially linear
portions: a first linear portion being substantially parallel to the
cylindrical axis of the scaffold (e.g., forming an angle between about 0
degree and about 20 degrees with respect to the cylindrical axis of the
scaffold); a second linear portion being substantially perpendicular to
the first linear portion (e.g., the second linear portion forming an
angle between about 70 degree and about 90 degrees with respect to the
first linear portion); and a third linear portion being substantially
parallel to the first linear portion (e.g., the third linear portion
forming an angle between about 0 degree and about 20 degrees with respect
to the first linear portion) or perpendicular to the second linear
portion (e.g., the third linear portion forming an angle between about 70
degree and about 90 degrees with respect to the second linear portion).

[0052] When the connection element is Z-shaped, it has a substantially
Z-shaped structure. When there is more than one connection element
between adjacent circumferential elements, the connection elements are
positioned symmetrically or asymmetrically at radial positions along the
circumference of the scaffold. If the connection elements are positioned
symmetrically, the radial distance between each pair of connection
elements, e.g., A-B and B-C, is equal.

[0053] The radial positions listed for the connection elements here are
only provided for illustration purposes and the connection elements may
be positioned by one of ordinary skill in the art without undue
experimentation at any point along the circumference of the scaffold with
respect to the cylindrical axis. For example, the positioning of the
connection elements may be determined by dividing 360° by n where
n is the number of connection elements between adjacent circumferential
elements. Where n =3, the connection elements may be positioned
symmetrically at approximately 120° intervals around the
circumference of the stent. When there are two equally spaced connection
elements between adjacent circumferential elements, they are situated
approximately 180° with respect to one another. In other words,
the two connection elements are oppositely oriented with respect to one
another.

[0054] For the purposes of reference only, the connection elements
connecting the circumferential elements in each pair are referred to as
first connection elements, while connection elements connecting the
circumferential elements in adjacent pairs of circumferential elements
are referred to as second connection elements. The first and second
connection elements may be of the same shape or have different shapes. In
addition, the shape of the first connection elements connecting the
circumferential elements in a pair of circumferential elements may be the
same or may very in both shape and length. Similarly, the connection
elements connecting adjacent pairs of circumferential elements may be the
same or may vary in shape and length. As discussed further below, the
first and second connection elements may be configured to allow the
vascular scaffold to expand without causing the circumferential elements
forming the pairs to significantly bend out of the plane formed by the
circumferential element after expansion. Thus, the connection elements
between adjacent pairs of circumferential elements (e.g., the second
connection elements) may be able to elongate in response to expansion of
the scaffold. In one embodiment, these connection elements have an
S-shape or are curvilinear.

[0055] When the scaffold is expanded, at least a portion of the connection
elements connecting the circumferential elements in the pairs and/or the
connection elements connecting the circumferential elements in adjacent
pairs form a contiguous spiral pattern. In one embodiment, the spiral
pattern comprises at least a portion of the first and second connection
elements. In another embodiment, the spiral pattern comprises at least a
portion of the first connection elements. In a third embodiment, the
spiral pattern comprises at least a portion of the second connection
elements. In a fourth embodiment, the spiral pattern comprises at least a
portion of the first and second connection elements, and at least a
portion of the circumferential elements. In a fifth embodiment, the
spiral pattern comprises at least a portion of the first connection
elements, and at least a portion of the circumferential elements. In a
sixth embodiment, the spiral pattern comprises at least a portion of the
second connection elements, and at least a portion of the circumferential
elements.

[0056] The length of a connection element refers to the absolute distance
of travel along the connection element starting from one end of the
connection element traveling along the distance to the other end of the
connection element.

[0057] The length of the second connection element can be greater than,
equal to or less than the length of the first connection element.

[0058] The undulations of the circumferential elements can form peaks and
valleys with respect to either proximal or distal end of the vascular
scaffold. The first connection elements can connect the circumferential
elements in the pair from peak to peak, peak to valley, or valley to
valley. Similarly, the second connection elements can connect the
circumferential elements between adjacent pairs from peak to peak, peak
to valley, or valley to valley. The peak to peak, peak to valley, or
valley to valley connections may be between circumferential elements that
are in the same cylindrical axial line or shifted by 180° degrees;
other shifts, include, but are not limited to, 5°, 60°,
90° and 120° degrees from the same cylindrical axial line.
The connection elements may connect any points on adjacent
circumferential elements, including, but not limited to, peak, valley,
any point on the ascending portion or descending portion of an
undulation.

[0059] The undulations of one circumferential element in a pair may either
be in phase or out of phase with the undulations of the other
circumferential element in the pair. If the two circumferential elements
are out of phase, the degree of phase difference may range from greater
than 0° to 180° degrees, including, but not limited to,
5°, 60°, 90° and 120° degrees.

[0060] Similarly, the undulations of one pair may either be in phase or
alternatively out of phase with the undulations of an adjacent pair. If
the two circumferential elements are out of phase the degree of phase
difference may range from greater than 0° to 180° degrees,
including, but not limited to, 5°, 60°, 90° and
120° degrees.

[0061] The undulations of adjacent circumferential elements may either be
in phase or out of phase. If the two circumferential elements are out of
phase, the degree of phase difference may range from greater than
0° to 180° degrees, including, but not limited to,
5°, 60°, 90°, 120 and 180° degrees.

[0062] When a radial expanding force is applied to the scaffold, such as
through an expandable balloon, the circumferential elements expand
radially and elongate circumferentially. Conversely, when an external
compressive force is exerted on the scaffold, the circumferential
elements contract radially and shorten circumferentially. When a radial
expanding force is applied to the scaffold, the undulations decrease in
amplitude. Conversely, when an external compressive force is exerted on
the scaffold, the undulation increases in amplitude.

[0063] In another embodiment, the scaffold comprises a plurality of
polygons. The polygon has n-sides where n is any positive integers. For
example, the polygons may have sides ranging from 3 to 30 (higher order
polygons are also encompassed by the designs of the present invention),
e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29 and 30 sided polygons, up to an
n-sided polygon. The sides of the polygons may be equal or unequal. The
opposite sides in a polygon may be substantially parallel to each other
when the scaffold is crimped. Opposite sides in a polygon may also take
other configurations in relation to each other.

[0064] The polygon may be formed from a plurality of undulations which are
connected by a plurality of connection elements. For example, the polygon
may be a hexagon formed from two undulations connected by two connection
elements; a hexagon may comprise a first undulation and a second
undulation, which are connected by a first segment and a second segment.
The filaments comprising the first and second undulations in each hexagon
may have different or identical width, length and thickness. The polygon
may also be formed from a plurality of undulations without connection
elements. For example, the polygons may be tetragons consisting of two
undulations. In higher-order polygons, e.g., n=8-30, the undulations may
be connected by a plurality of connection elements.

[0065] An undulation may comprise one segment or at least two segments.
The segments may be linear or curvilinear. When a segment is curvilinear,
the degree of curvature may vary. A segment may be concave or convex. A
segment may contain solely linear portions joined together, or solely
curved portions joined together. Alternatively, a segment may contain
both linear portions and curved portions that are joined together. The
segment may comprise at least one bend placed at selected points along
its length. For example, a segment may take the shape of a stylized n, C,
U, V, etc. A segment may also be in the shape of a loop where the loop
may be circular or semicircular. The segment can essentially assume any
suitable configuration. The length, width and thickness of the segments
of the undulations may be equal or unequal. The two undulations of each
polygon across each circumferential component may be identical or may
vary. A wide variety of different configurations for the polygons as well
as the various segments representing the sides of the polygon are
encompassed by the present invention. For example, the segments
representing the sides of the polygon may be linear or curvilinear. In
one polygon, the length of the segments comprising one undulation may be
equal to or greater than the length of the segments of the opposing
undulation. The polygon may be convex (i.e., all its interior angles are
less than)180° or non-convex (i.e., it contains at least one
interior angle greater than) 180°. The polygons can form a
continuous, interconnected structure across the body of the scaffold. A
circumferential element (or a pair of circumferential elements) may
contain different or substantially identical polygons. The polygons of
different circumferential element may be different or substantially
identical. The surface area of adjacent polygons may be equal or unequal.
The surface area of the polygons, i.e., the area encompassed by the
sides, can be calculated mathematically from the length of the sides of
the polygon. http://mathworld.wolfram.com/PolygonArea.html, April, 2009.

[0066] One embodiment of the scaffold of the present invention is
illustrated in FIG. 1. The pairs of circumferential elements are shown as
1-4. The circumferential elements in the scaffold for pairs 1-4 are
labeled in parentheses, 1(5, 6), 2(7, 8), 3(9, 10) and 4(11, 12). The
connection elements (first connection elements) between two
circumferential elements in one pair, 1, are shown as 13-18, while the
connection elements between adjacent pairs of circumferential elements 1
and 2 (second connection elements) are shown as 19-21. The scaffold may
contain a marker dot, 22. Polygons formed by the undulations and the
connection elements of the scaffold are illustrated by the boxes at 23
and 24.

[0067] A second embodiment of the scaffold is shown in FIG. 2A, here, the
circumferential elements of the scaffold vary in length. The
circumferential length of the circumferential elements are A>B>C;
however, this order of lengths is shown only for illustration purposes.
The amplitude of the undulations formed by the circumferential elements
A, B, C, in a partially crimped or fully crimped state also has the
length or height of A'>B'>C' (FIG. 2B). In the embodiment shown,
the circumferential elements with varying lengths are distributed along
the body of the scaffold as follows: A-B (25, 26), C-C (27, 28), C-C (29,
30), C-B (31, 32), B-B (33, 34), B-B (35, 36), and B-A (37, 38). However,
numerous other combinations and distributions are possible as well. FIG.
2C shows a repeating sinusoidal pattern where the amplitude of the
undulations is constant across the circumferential element. FIG. 2D shows
a non-repeating sinusoid pattern. In a non-repeating sinusoid pattern,
the amplitude and/or ordinary frequency of the undulations may vary
either systematically or randomly along the circumference of the
circumferential element.

[0068] The length of a circumferential element refers to the absolute
distance of travel along the circumferential element starting from an
artificial point on the circumferential element and back around to the
same artificial point.

[0069] A detailed view of one part of the undulations forming two adjacent
pairs of circumferential elements is shown in FIG. 3. The circumferential
elements are shown as 39, 40. They are connected by a connection element
(second connection element), which has two linear portions, 41, 43 and an
S-shaped portion 42. The undulations of the circumferential element 40
have amplitudes 43 and 44. In the embodiment shown, 44 is greater than
43.

[0070] FIG. 4A shows the details of the connection elements (first
connection elements) at one end of the scaffold. Circumferential elements
46, 47 are connected by connection elements (first connection elements)
48-55. FIG. 4B illustrates various embodiments of where the marker dot,
54, can be attached to the connection element, 56-59, at various points
along the connection element 53. FIG. 4C shows a perspective view of a
marker dot 251. FIG. 4D shows cross sections of various embodiments of
marker dot 252. The section of a scaffold for a marker dot can take
various forms, including, but not limited to, a see-through void (252), a
cup-shaped structure with a hole in the bottom (253), and a cup-shaped
structure (254).

[0071] FIGS. 5A-5C show the scaffold in an orthogonal (5A), side (5B) and
end (5C) views. The circumferential elements are labeled 60-64 and 65-70.
The connection elements between pairs of circumferential elements are
shown as 71, 72, 74, 75 (first connection element), while the connection
element between two pairs is labeled 73. The formation of the spiral
design is shown as 76-78 and contains the connection elements between
pairs of circumferential elements as well as the connection elements
between circumferential elements forming the pair (first and second
connection elements, respectively). The circumferential elements forming
a pair are shown with highlighted lines 63, 64.

[0072]FIG. 6 shows a cut pattern of another embodiment of the scaffold.
The circumferential elements are labeled 79-92, with the pairs of
circumferential elements being shown as 79,80; 81,82; 83,84; 85,86; 87,
88; 89,90 and 91, 92. The spiral pattern is shown as 93-103 and comprises
an alternating pattern of connection elements between pairs of
circumferential elements (second connection elements), 93, 95, 97, 99,
101 and 103, with connection elements between the circumferential
elements forming a pair (first connection elements), 94, 96, 98, 100 and
102. In the inset to FIG. 6, a partially compressed view of the scaffold
is shown. The circumferential elements are labeled 107, 107', while the
connection elements are labeled 105, 106. The scaffold shown in the
figure contains more than one spiral pattern, 108-110 which may be
substantially parallel to one another.

[0073] FIG. 7 shows a cut pattern of the scaffold with an alternative
spiral pattern. In this embodiment, the spiral pattern is formed from an
alternating pattern of connection elements between pairs of
circumferential elements (first connection elements), 112, 115, 118, 121,
portions of the undulations of the circumferential elements, 113, 117,
120, and connection elements connecting two adjacent pairs of
circumferential elements (second connection elements), 111, 114, 116,
119, 122. In this embodiment, the spiral pattern has the following
repeating sequence starting from one end of the scaffold: first
connection element, second connection element, portion of the undulation,
first connection element, second connection element, portion of the
undulation, which is repeated across the scaffold. Other repeating
sequences are possible, including, but not limited to, (a) first
connection element, portion of the undulation, first connection element,
repeated n times across the body of the scaffold; (b) first connection
element, portion of the undulation, repeated n times across the body of
the scaffold; (c) second connection element, portion of the undulation,
repeated n times across the body of the scaffold; or (d) second
connection element, portion of the undulation, second connection element,
repeated n times across the body of the scaffold;

[0074]FIG. 8 shows an embodiment where the connection elements have a
variety of different shapes and the distribution of the pattern of the
connection elements varies across the body of the scaffold. Specifically,
in the embodiment shown, the connection elements between pairs of
circumferential elements, are linear, 124-126 and 130-132 or curvilinear,
127-129, 134-136 and 137-139. One of the curvilinear connection elements
between pairs of circumferential elements have both linear and
curvilinear portions, 127-129. As is evident from the illustration, the
pattern of connection elements can vary across the body of the scaffold,
curvilinear, 137-139, 134-136, linear, 130-132, curvilinear, 127-129 and
linear, 124-126. Other possible arrangements as well as geometric shapes
are encompassed by the invention. One of ordinary skill in the art can
select the sequence and type of connection elements to fit the
flexibility and spatial requirements posed by the vasculature.

[0075]FIG. 9 shows a cut pattern of the scaffold with an alternative
spiral pattern together with circumferential elements of varying length.
This embodiment illustrates the modular design nature of the scaffold
where circumferential elements of differing lengths as well as a variety
of different connection elements are combined to form a scaffold having
two different spiral patterns. The circumferential elements have lengths,
An, Bn and Cn. For example, in one embodiment, the
circumferential lengths are A>B>C. Specifically, A1 and A0 (140,
144) are combined with B0-B5 (141, 143) which in turn are
combined with C0-C6 (142) in the sequence shown in FIG. 9.
There are two different spiral patterns present in this embodiment,
145-147, and 153-154. The spiral pattern in 147 comprises a connection
element between the circumferential elements forming the pair (first
connection elements), 148, 150, 152 and the connection element between
pairs of circumferential elements (second connection elements), 149, 151.
The other spiral pattern, 154, comprises a connection element between the
circumferential elements forming the pair (first connection elements),
155, 158, a portion of the undulation of the circumferential element,
157, 160 and the connection element between pairs of circumferential
elements (second connection elements), 156, 159.

[0076] FIGS. 10A and 10B show side views of a three-dimensional
perspective of the scaffold in a crimped or compressed state. The pairs
of circumferential elements are shown as 172,173. One undulation forming
part of a circumferential element 161,167 is adjacent to a connection
element between the pairs of circumferential elements 162, 166 (the
second connection element). This connection element sits on top or
nestles/nests, but does not necessarily touch, the undulation of a
circumferential element in an adjacent pair 163, 171. The connection
elements connecting the circumferential elements in a pair are shown as
169, 170 (the first connection element). This arrangement can also be
seen clearly in FIG. 10B where one undulation forming part of a
circumferential element 175,186 is adjacent to a connection element
between the pairs of circumferential elements 176, 185 (the second
connection element). This connection element sits on top or nestles/nests
the undulation of a circumferential element in an adjacent pair 180, 184.
The connection elements connecting the circumferential elements in a pair
are shown as 182 (the first connection element). A pair of
circumferential elements is labeled as 183.

[0077]FIG. 11A shows a cut pattern of the scaffold with an alternative
spiral pattern. The circumferential elements are labeled 458-464, with
the pairs of circumferential elements being shown as 458, 459; 460, 461
and 462, 463. In this embodiment, the spiral pattern is formed from an
alternating pattern of connection elements between pairs of
circumferential elements (first connection elements), 451, 455, portions
of the undulations of the circumferential elements, 452, 454, 456, and
connection elements connecting two adjacent pairs of circumferential
elements (second connection elements), 453, 457. In this embodiment, the
spiral pattern has the following repeating sequence starting from one end
of the scaffold: first connection element, portion of the undulation,
second connection element, portion of the undulation, which is repeated
across the scaffold. In FIG. 11A, both the first and second connection
elements are linear.

[0078] FIG. 11B shows a cut pattern of the scaffold with another spiral
pattern. The circumferential elements are labeled 465-472, with the pairs
of circumferential elements being shown as 465, 466; 467, 468; 469, 470
and 471, 472. In this embodiment, the spiral pattern is formed from an
alternating pattern of connection elements connecting two adjacent pairs
of circumferential elements (second connection elements), 473, 477,
portions of the undulations of the circumferential elements, 474, 476,
478, and connection elements between pairs of circumferential elements
(first connection elements), 475, 479. In this embodiment, the spiral
pattern has the following repeating sequence starting from one end of the
scaffold: second connection element, portion of the undulation, first
connection element, portion of the undulation, which is repeated across
the scaffold. In FIG. 11B, both the first and second connection elements
are S-shaped.

[0079] One of the issues with the prior art designs is that, when the
scaffold expands, the undulations forming adjacent circumferential
elements are distorted. The present design is an improvement.

[0080]FIG. 12 illustrates the functionality of the connection element
between adjacent pairs of circumferential elements. 199 and 200 are pairs
of circumferential elements. Three types of connection elements are
illustrated, linear, 201 and curvilinear 202, 203. When the scaffold
expands, connection element 201 is restrictive and cannot accommodate
expansion of the circumferential elements; however, either connection
element 203 or 203 are less restrictive and accommodate expansion without
distorting the circumferential elements in adjacent pairs out of the
plane, 197, 198.

[0081]FIG. 13 illustrates the geometry of the scaffold and the connection
elements on expansion. The pairs of circumferential elements are shown as
206, 207. The connection elements between the undulations (first
connection element) forming the pairs of circumferential elements are
labeled 208-210. The connection element between pairs is labeled 213. The
geometry of expansion is illustrated by creating a triangle with 213
using 211,212. The angle formed with respect to the cylindrical axis for
208 and 210 is labeled 215, 216. The angle formed with 211, 212 and 213
is labeled 214. After expansion, the angles 214', 215' and 216' all
increase.

[0083]FIG. 14c shows that, with one end of the connection elements being
attached to a point on an undulation of a circumferential element, the
other end of the connection element may be attached to the direct
corresponding peak or valley of the adjacent circumferential element, or
to a point shifted by 1, 2, 3, 4, 5, 6, 7, 8, 9 . . . N (N can be any
positive integers) undulations (the shift may be towards either
directions). In FIG. 14c, the two ends of the connection elements are:
480 (peak), 481 (valley); 482 (peak), 483 (valley shifted by 1
undulation); 484 (peak), 485 (valley shifted by 1 undulation); 486
(valley), 487 (peak).

[0084] FIGS. 15A-E illustrates where the connection elements can attach
along the undulations. The connection elements here are shown as linear;
however, this shape is only shown for illustration purposes and the
connection elements can be curvilinear or S-shaped or any other shape
encompassed by the invention. The embodiments shown here can apply to
both the first and second connection elements. The cylindrical axis of
the scaffold is shown as well. The connection element 220 can be attached
to the valley of one undulation, 221, and the peak of another undulation,
222 (FIG. 15A). Alternatively, the connection elements 224 can be
attached on either side of the valley or peak of two undulations 223, 225
(FIG. 15B). The connection element 227 can be attached to the valleys
226, 228 of two undulations (FIG. 15C). The connection element 230 can
also be attached to the peak 229, and valley 231 of two undulations (FIG.
15D). The connection element 234 can also be attached to the ascending
portions 232, 235 of two undulations (FIG. 15E). The figures shown here
illustrate the connection element attached to an opposing undulation;
however, the connection element can be attached to undulations that are
shifted radially with respect to the cylindrical axis (FIG. 16)
(236-238).

[0085] The proximal and distal ends of the scaffold are labeled with
respect to the heart with the proximal end closest to the aortic valve.
The terms peak and valley are arbitrarily defined with respect to the
proximal and distal ends of the scaffold.

[0086] FIGS. 17A and 17B show an example of phasing in adjacent
circumferential elements. In FIG. 17A, the circumferential elements 239,
240 are in-phase with each other (compare cylindrical axial lines for 243
and 244). In contrast, in FIG. 17B, the circumferential elements 242, 247
are 180° out-of-phase with each other (compare 245 and 248).

[0087]FIG. 18 shows a cut pattern of another embodiment of the scaffold.
The circumferential elements are labeled 301-308, with the pairs of
circumferential elements being shown as 301, 302; 303, 304; 305, 306; and
307, 308. The spiral pattern is shown as 309-317 and comprises an
alternating pattern of connection elements between pairs of
circumferential elements (second connection elements), 309, 311, 313, 315
and 317, with connection elements between the circumferential elements
forming a pair (first connection elements), 310, 312, 314 and 316. The
scaffold shown in the figure contains more than one spiral pattern,
318-320.

[0088]FIG. 19A shows a cut pattern of another embodiment of the scaffold.
The circumferential elements of this embodiment are comprised of a
plurality of linear segments. The circumferential elements are labeled
321-330, with the pairs of circumferential elements being shown as 321,
322; 323, 324; 325, 326; 327, 328 and 329, 330. The spiral pattern is
shown as 331-340 and comprises an alternating pattern of connection
elements between pairs of circumferential elements (second connection
elements), 331, 333, 335, 337 and 339, with connection elements between
the circumferential elements forming a pair (first connection elements),
332, 334, 336, 338 and 340. In the spiral or helical patterns shown the
spiral pattern cuts-across the circumferential elements.

[0089] Detailed views of parts of the scaffold in FIG. 19A are shown in
FIGS. 19B-19E. In FIG. 19D, the circumferential elements in a pair are
shown as 353, 354. They are connected by connection elements (first
connection elements), 355, 356. In FIG. 19D, a circumferential element is
shown to be comprised of a plurality of linear segments, 341-352. In FIG.
19E, circumferential elements 357, 358 are connected by connection
elements (second connection elements) 359, 360.

[0090]FIG. 19G shows a side view of the scaffold. The circumferential
elements are labeled 361-368, forming pairs 374-377. The connection
elements between circumferential elements within a pair (first connection
element) are shown as 369, 371, 373, while the connection element between
two pairs of circumferential elements are labeled 370, 372. The formation
of the spiral design is shown as 369-373 and contains the connection
elements between adjacent pairs of circumferential elements (second
connection elements) as well as the connection elements between
circumferential elements forming the pair (first connection elements).

[0091] Scaffolds of the present invention may employ one, two or more end
zones. The end zone may take numerous forms. An end zone may be formed
from one or a plurality of circumferential elements and is connected to
the main body at one or more bridging elements. Adjacent circumferential
elements may be connected directly, or may be connected by at least one
second connection element. In one embodiment, an end zone contains a
first and second circumferential element.

[0092] The scaffold may further comprise at least one radiopaque marker.
See, www.nitinol-europe.com/pdfs/stentdesign.pdf for a review of the
design and makeup of radiopaque markers which are well known in the art.
The radiopaque markers may assume a variety of different sizes and
shapes. For example, a radiopaque marker may contain a centrally placed
marker hole. The marker hole may be circular or semicircular, but may
also assume other shapes, such as a semicircular hole with an extrusion
or dimple positioned at one portion of the circumference, or a hole in
the shape of a heart.

[0093] The radiopaque marker may be electron-dense or x-ray refractile
markers, such as metal particles or salts. Non-limiting examples of
suitable marker metals include iron, gold, colloidal silver, zinc and
magnesium, either in pure form or as organic compounds. Other radiopaque
materials are tantalum, tungsten, platinum/iridium, or platinum. Heavy
metal and heavy earth elements are useful in variety of compounds such as
ferrous salts, organic iodine substances, bismuth or barium salts, etc.
Further embodiments that may be utilized may encompass natural
encapsulated iron particles such as ferritin that may be further
cross-linked by cross-linking agents. Ferritin gel can be constituted by
cross-linking with low concentrations (0.1-2%) of glutaraldehyde. The
radiopaque marker may be constituted with a binding agent of one or more
biodegradable polymer, such as PLLA, PDLA, PLGA, PEG, etc. In one
embodiment comprising a radiopaque marker, iron containing compounds or
iron particles are encapsulated in a PLLA polymer matrix to produce a
pasty substance, which can be injected or otherwise deposited in the
hollow receptacle contained about the stent.

[0094] The scaffolds may also have a transition zone between the end zone
and the main body. The transition zone may be formed from a plurality of
undulations, each undulation comprising two adjacent connection elements
connected by a loop with the width of the loop varying across the
transition zone. The transition zone may comprise a plurality of polygons
where the surface area of adjacent polygons in the transition zone
increases circumferentially. U.S. Patent Publication No. 20110125251. The
transition zone may take other suitable configurations.

[0095] The dimensions of the scaffold may vary from about 10 mm to about
300mm in length, from 20 mm to about 300 mm in length, from about 40 mm
to about 300 mm in length, from about 20 mm to about 200 mm in length,
from about 60 mm to about 150 mm in length, or from about 80 mm to about
120 mm in length. The internal diameter (I.D.) of the stent may range
from about 2 mm to about 25 mm, from about 2 mm to about 5 mm (e.g., for
the coronary arteries), from about 4 mm to about 8 mm (e.g., for
neurological spaces in the CNS, both vascular and nonvascular), from
about 6 mm to about 12 mm (e.g., for the iliofemoral), from about 10 mm
to about 20 mm (e.g., for the ilioaortic) and from about 10 mm to about
25 mm (e.g., for the aortic).

[0096] The device of the present invention may be used as a self-expanding
stent or with any balloon catheter stent delivery system, including
balloon catheter stent delivery systems described in U.S. Pat. Nos.
6,168,617, 6,222,097, 6,331,186 and 6,478,814. In one embodiment, the
present device is used with the balloon catheter system disclosed in U.S.
Pat. No. 7,169,162.

[0097] The scaffold of the present invention may be used with any suitable
catheter, the diameter of which may range from about 0.8mm to about 5.5
mm, from about 1.0 mm to about 4.5 mm, from about 1.2 mm to about 2.2 mm,
or from about 1.8 to about 3 mm. In one embodiment, the catheter is about
6 French (2 mm) in diameter. In another embodiment, the catheter is about
5 French (1.7 mm) diameter.

[0098] The scaffold may be inserted into the lumen of any vessel or body
cavity expanding its cross-sectional lumen. The invention may be deployed
in any artery, vein, duct or other vessel such as a ureter or urethra and
may be used to treat narrowing or stenosis of any artery, including, the
coronary, infrainguinal, aortoiliac, subclavian, mesenteric or renal
arteries. Other types of vessel obstructions, such as those resulting
from a dissecting aneurysm are also encompassed by the invention. The
subjects that can be treated using the scaffolds and methods of this
invention are mammals, including a human, horse, dog, cat, pig, rabbit,
rodent, monkey and the like.

[0099] The scaffold of the present invention may be formed from at least
one bioabsorbable polymer representing a wide range of different polymers
which is capable of crystallizing. Typically, bioabsorbable polymers
comprise aliphatic polyesters based on lactide backbone such as poly
L-lactide (PLLA), poly D-lactide (PDLA), poly D,L-lactide, mesolactide,
glycolides, lactones, as homopolymers or copolymers, as well as formed in
copolymer moieties with co-monomers such as, trimethylene carbonate (TMC)
or ε-caprolactone (ECL). U.S. Pat. Nos. 6,706,854 and 6,607,548;
EP 0401844; and Jeon et al. Synthesis and Characterization of
Poly(L-lactide)-Poly(ε-caprolactone). Multiblock Copolymers
Macromolecules 2003: 36, 5585-5592. The copolymers comprises a moiety
such as L-lactide or D-lactide of sufficient length that the copolymer
can crystallize and not be sterically hindered by the presence of
glycolide, polyethylene glycol (PEG), ε-caprolactone,
trimethylene carbonate or monomethoxy-terminated PEG (PEG-MME). For
example, in certain embodiments greater than 10, 100 or 250 L or
D-lactides may be arrayed sequentially in the polymer. The stent may also
be composed of bioabsorbable polymeric compositions such as those
disclosed in U.S. Pat. Nos. 7,846,361; 7,897,224 and 8,137,603; and
applicant's co-pending U.S. Patent Publication No. 2010/0093946.

[0100] Based on the presence of the monomer type, the following polymer
nomenclature can be used.

[0101] In an embodiment of the present invention, the composition
comprises a base polymer of poly(L-lactide) or poly(D-lactide). Other
base polymer compositions include blends of poly(L-lactide) and
poly(D-lactide). Other advantageous base polymer compositions include
poly(L-lactide-co-D,L-lactide) or poly(D-lactide-co-D,L-lactide) with a
D,L-lactide co-monomer molar ratio from 10 to 30%, and
poly(L-lactide-co-glycolide) or poly(D-lactide-co-glycolide) with a
glycolide co-monomer molar ratio from 10 to 20%.

[0102] Another embodiment embodies a base polymer featuring a
poly(L-lactide) moiety, and/or a poly(D-lactide) moiety, linked with a
modifying copolymer thereof, including
poly(L-lactide-co-tri-methylene-carbonate or
poly(D-lactide-co-tri-methylene-carbonate) and
(L-lactide-co-ε-caprolactone), or
poly(D-lactide-co-ε-caprolactone), in the form of block
copolymers or blocky random copolymers, wherein the lactide chain length
is sufficient to effect cross-moiety crystallization. Cross moiety
crystallization of compositions with copolymers affords increased modulus
data in tensile tests avoiding the method for reducing the tensile
strength in the polymer blend.

[0103] The polymer composition can allow for the development of the
lactide racemate (stereo complex) crystal structure, between the L and D
moieties, to further enhance the mechanical properties of the
bioabsorbable polymer medical device. The formation of the racemate
(stereo complex) crystal structure can accrue from formulations such as
combinations of:

[0104] Poly L-lactide with Poly D-lactide with Poly
L-lactide-co-TMC;

[0105] Poly D-lactide with Poly L-lactide-co-TMC;

[0106] Poly L-lactide with Poly D-lactide-co-TMC;

[0107] Poly L-lactide
with Poly D-lactide with Poly D-lactide-co-TMC;

[0108] Poly
L-lactide-co-PEG with Poly D-lactide-co-TMC; and

[0109] Poly
D-lactide-co-PEG with Poly L-lactide-co-TMC.

[0110] Poly-lactide racemate compositions can be "cold formable or
bendable" without adding additional heat. Cold-bendable scaffolds of the
invention do not require beating to become flexible enough to be crimped
onto a carrier device or accommodate an irregularly shaped organ spaces.
Cold bendable ambient temperatures are defined as room temperature not
exceeding 30° C. Cold-bendable scaffolds can afford sufficient
flexibility when implanted allowing for an expanded scaffold device in an
organ space such as pulsating vascular lumen. For example, in terms of a
stent, it may be desirable to utilize polymeric compositions that afford
mostly amorphous polymer moieties after fabrication that can crystallize
particularly when the secondary nested or end-positioned meandering
connection elements when the scaffold is strained by stretching upon
balloon expansion for implantation. Such cold-bendable polymeric scaffold
embodiments of are not brittle and do not have to be preheated to a
flexible state prior to implantation onto a contoured surface space in
the body. Cold-bendability allows these blends to be crimped at room
temperature without crazing, and moreover, the blends can be expanded at
physiological conditions without crazing.

[0111] Poly-lactide racemate compositions and non-racemate compositions of
embodiments herein may be processed to have blocky moieties allowing
cross moiety crystallization even with the addition of an impact modifier
to the blend composition. Such a blend introduces the possibility to
design device specific polymer compositions or blends by producing either
single or double Tg's (glass melt transition points).

[0112] As is understood in this art, polymer compositions of the present
invention can be customized to accommodate various requirements of the
selected medical device. The requirements include mechanical strength,
elasticity, flexibility, resilience, and rate of degradation under
physiological and localized anatomical conditions. Additional effects of
a specific composition concern solubility of metabolites, hydrophilicity
and uptake of water and any release rates of matrix attached or enclosed
pharmaceuticals.

[0114] The scaffold fashioned from the polymer compositions above may be
significantly amorphous post extrusion or molding. The scaffold may be
subjected to controlled re-crystallization to induce incremental amounts
of crystallinity and mechanical strength enhancement. Further
crystallization can be induced by strain introduction at the time of
device deployment. Such incremental re-crystallization may be employed
either on a scaffold "blank" prior to secondary or final fabrication
(such as by laser cutting) or post such secondary fabrication.
Crystallization (and thus mechanical properties) can also be maximized by
strain induction such as by "cold" drawing polymeric tubing, hollow
fiber, sheet or film, or monofilament prior to further fabrication.
Crystallinity has been observed to contribute a greater stiffness in the
scaffold. Therefore, the polymer composition and steric complex of the
scaffold has both amorphous and paracrystalline moieties. The initially
semicrystalline polymer portion can be manipulated by the action of
stretching or expansion of a given device. Yet an adequate amount of
amorphous polymeric character is desirable for flexibility and elasticity
of the polymeric device. The usual monomer components include lactide,
glycolide, caprolactone, dioxanone, and trimethylene carbonate. The
scaffold may also be constructed to allow relatively uniform exposure to
local tissue or circulatory bioactive factors and enzymes perfusing and
acting on the polymer structure during bioabsorption.

[0115] The rate of in situ breakdown kinetics of the polymeric matrix of
an organ space implant, such as a cardiovascular stent, is sufficiently
gradual to avoid tissue overload, inflammatory reactions or other more
adverse consequences. In an embodiment, the scaffold is fabricated to
survive at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 24 or 36 months.

[0116] Pharmaceutical compositions may be incorporated within the polymers
by, for example, grafting to the polymer active sites, or coating. An
embodiment of the polymer according to the invention affords attachment
or incorporation the biological healing factors or other drugs in the
polymeric matrix or a polymer coating.

[0117] In another embodiment, the composition may be constructed to
structurally enclose or attach to drugs in the polymeric matrix. The
purpose of such additives may to provide, for example with respect to a
stent, treatment of the cardiovascular system or in vascular site in
contact with the medical device polymer. The kind of enclosure or
attachment of drugs in the polymer may determine the rate of release form
the scaffold. For example, the drug or other additive may be bound in the
polymer matrix by various known methods including but not limited to
covalent bonds, non-polar bonds as well as an ester or similar
bioreversible bonding means.

[0118] In one embodiment, a bioabsorbable implantable medical device may
be covered with a biodegradable and bioabsorbable coating containing one
or more barrier layers where the polymer matrix contains one or more of
the aforementioned pharmaceutical substances. In this embodiment, the
barrier layer may comprise a suitable biodegradable material, including
but not limited to, suitable biodegradable polymers including: polyesters
such as PLA, PGA, PLGA, PF, PCL, PCC, TMC and any copolymer of these;
polycarboxylic acid, polyanhydrides including maleic anhydride polymers;
polyorthoesters; poly-amino acids; polyethylene oxide; polyphosphacenes;
polylactic acid, polyglycolic acid and copolymers and mixtures thereof
such as poly(L-lactic acid) (PLLA), poly(D,L-lactide), poly(lactic
acid-co-glycolic acid), 50/50 (DL-lactide-co-glycolide); polydixanone;
polypropylene fumarate; polydepsipeptides; polycaprolactone and
co-polymers and mixtures thereof such as
poly(D,L-lactide-co-caprolactone) and polycaprolactone co-butylacrylate;
polyhydroxybutyrate valerate and blends; polycarbonates such as
tyrosine-derived polycarbonates and arylates, polyiminocarbonates, and
polydimethyltrimethyl-carbonates; cyanoacrylate; calcium phosphates;
polyglycosaminoglycans; macromolecules such as polysaccharides (including
hyaluronic acid; cellulose, and hydroxypropylmethyl cellulose; gelatin;
starches; dextrans; alginates and derivatives thereof), proteins and
polypeptides; and mixtures and copolymers of any of the foregoing. The
biodegradable polymer may also be a surface erodable polymer such as
polyhydroxybutyrate and its copolymers, polycaprolactone, polyanhydrides
(both crystalline and amorphous), maleic anhydride copolymers, and
zinc-calcium phosphate. The number of barrier layers that the polymeric
scaffold on a device may have depends on the amount of therapeutic need
as dictated by the therapy required by the patient. For example, the
longer the treatment, the more therapeutic substance required over a
period of time, the more barrier layers to provide the pharmaceutical
substance in a timely manner.

[0119] In another embodiment, the additive in the polymer composition may
be in the form of a multiple component pharmaceutical composition within
the matrix such as containing a last release pharmaceutical agent to
retard early neointimal hyperplasia/smooth muscle cell migration and
proliferation, and a secondary biostable matrix that releases a long
acting agent for maintaining vessel patency or a positive blood vessel
remodeling agent, such as endothelial nitric oxide synthase (eNOS),
nitric oxide donors and derivatives such as aspirin or derivatives
thereof, nitric oxide producing hydrogels, PPAR agonist such as
PPAR-α gands, tissue plasminogen activator, statins such as
atorvastatin, erythropoietin, darbepotin, serine proteinase-1 (SERP-1)
and pravastatin, steroids, and/or antibiotics.

[0120] Pharmaceutical compositions may be incorporated into the polymers
or may be coated on the surface of the polymers after mixing and
extrusion by spraying, dipping or painting or microencapsulated and then
blended into the polymer mixture. U.S. Pat. No. 6,020,385. If the
pharmaceutical compositions are covalently bound to the polymer blend,
they may be linked by hetero- or homo-bifunctional cross linking agents
(see, http://www.piercenet.com/products/browse.cfm?fldID=020306).

[0123] The stent may also be coated with at least one type of antibodies.
For example, the stent may be coated with antibodies or polymeric
matrices which are capable of capturing circulating endothelial cells.
U.S. Pat. No. 7,037,772 (see also, U.S. Patent Publications Nos.
20070213801, 200701196422, 20070191932, 20070156232, 20070141107,
20070055367, 20070042017, 20060135476, 20060121012).

[0124] The scaffold of the present invention may also be formed from metal
such as nickel-titanium (Ni--Ti). A metal composition and process of
manufacturing the device is disclosed in U.S. Pat. No. 6,013,854. The
super elastic metal for the device is preferably a super elastic alloy. A
super elastic alloy is generally called "a shape-memory alloy" and
resumes its original shape after being deformed to such a degree that an
ordinary metal undergoes permanent deformation. Super elastic alloys
useful in the invention include: Elgiloy® and Phynox® spring
alloys (Elgiloy® alloy is available from Carpenter Technology
Corporation of Reading Pa.; Phynox® alloy is available from Metal
Imphy of Imphy, France), 316 stainless steel and MP35N alloy which are
available from Carpenter Technology corporation and Latrobe Steel Company
of Latrobe, Pa., and superelastic Nitinol nickel-titanium alloy which is
available from Shape Memory Applications of Santa Clara, Calif. U.S. Pat.
No. 5,891,191.

[0125] The scaffold of the present invention may be manufactured in
numerous ways. The device may be formed from a tube by removing various
portions of the tube's wall to form the patterns described herein. The
resulting device will thus be formed from a single contiguous piece of
material, eliminating the need for connecting various segments together.
Material from the tube wall may be removed using various techniques
including laser (YAG laser for example), electrical discharge, chemical
etching, metal cutting, a combination of these techniques, or other well
known techniques. U.S. Pat. Nos. 5,879,381 and 6,117,165 which are hereby
incorporated in their entirety by reference. Forming stents in this
manner allows for creation of a substantially stress-free structure. In
particular, the length may be adapted to that of the diseased part of the
lumen in which the stent is to be placed. This may avoid using separate
stents to cover the total diseased area.

[0126] In an alternate embodiment, a method for fabricating a tube-shaped
stent comprising: preparing a racemic poly-lactide mixture; fabricating a
biodegradable polymer tube of the racemic poly-lactide mixture; laser
cutting the tube until such scaffold is formed. In this embodiment, the
fabrication of the scaffold can be performed using a molding technique,
which is substantially solvent-free, or an extrusion technique.

[0127] Reference is also made, and thereby incorporated in their entirety
into this application, to U.S. Pat. Nos. 7,329,277, 7,169,175, 7,846,197,
7,846,361, 7,833,260, 6,0254,688, 6,254,631, 6,132,461, 6,821,292,
6,245,103 and 7,279,005. In addition, U.S. patent application Ser. Nos.
11/781,230, 12/507,663, 12/508,442, 12/986,862, 11/781,233, 12/434,596,
11/875,887, 12/464,042, 12/576,965, 12/578,432, 11/875,892, 11/781,229,
11/781,353, 11/781,232, 11/781,234, 12/603,279, 12/779,767 and
11/454,968, as well as U.S. Patent Publication No. 2001/0029397, are also
incorporated in their entirety.

[0128] The scope of the present invention is not limited by what has been
specifically shown and described hereinabove. Those skilled in the art
will recognize that there are suitable alternatives to the depicted
examples of materials, configurations, constructions and dimensions.
Numerous references, including patents and various publications, are
cited and discussed in the description of this invention. The citation
and discussion of such references is provided merely to clarify the
description of the present invention and is not an admission that any
reference is prior art to the invention described herein. All references
cited and discussed in this specification are incorporated herein by
reference in their entirety. Variations, modifications and other
implementations of what is described herein will occur to those of
ordinary skill in the art without departing from the spirit and scope of
the invention. While certain embodiments of the present invention have
been shown and described, it will be obvious to those skilled in the art
that changes and modifications may be made without departing from the
spirit and scope of the invention. The matter set forth in the foregoing
description and accompanying drawings is offered by way of illustration
only and not as a limitation.